The use of predetermined and prepackaged doses in the form of refills containing ground coffee for preparing espresso type or similar drinks has many advantages, including those of facilitating the operations of preparing the drink, of ensuring a relatively clean preparation and of controlling a relatively constant dose and quality of the prepared product.
The principle of extraction from closed or sealed refills includes: (i) enclosing the refill in a sealed chamber, (ii) piercing one face of the refill, (iii) introducing a quantity of hot water into the refill so as to create a pressurized environment inside the refill in order to produce the coffee extract, (iv) then releasing the coffee extract through the opposite face of the refill which, in contact with projecting parts of the device, opens under the effect of the internal pressure.
There are already devices for extraction from capsules or cartridges, comprising a housing for the cartridge to be extracted and a point such as those described in U.S. Pat. Nos. 4,136,202 and 6,026,732. In these devices, the point has a dual function. On the one hand, it opens the upper part of the capsule and, on the other hand, it forms the inlet channel for water in the sense that the water is directly introduced inside the capsule through the point itself. One drawback of such a device arises in that the hole obtained by a single needle has the effect of creating, at the beginning of the extraction, a preferred pathway through the mass of coffee to be extracted without completely wetting it. The consequence of creating a preferred pathway is that when the extraction takes place, the rate at which the pressure rises becomes too high, which may lead to releasing the extract too early such that not enough extraction time is obtained. Of course, the consequence may be a loss of solids and flavors which then remain fixed in the grounds and are therefore not transferred to the extract. Another drawback arises in that the point tends to get blocked quickly because of the scale in the water or contact with the grounds, which may affect the performance of the device. Given the large size of the hole made in the capsule, the capsule is also subject to undesirable rise of the grounds and the liquid residue after use.
U.S. Pat. Nos. 5,649,472, 5,762,987, and 5,826,492 also relate to devices which have means of perforating a flexible sachet containing the product to be extracted, which is in the form of a grid for distributing water provided on its lower face with elements having projecting points, blades, or crosses. Orifices may be provided for the passage of water through the distribution grid at each perforating means. Thus, an improvement in the water distribution in the sachet is provided which makes it possible to improve the wetting of the mass to be extracted. The orifices with a closed section can, however, fur up over time with which affects the control of the flow rate and pressure during the extraction.
U.S. Pat. No. 5,794,519 relates to an extraction device comprising an extraction head which supports movable needles by means of an ejector which ejects the capsule from the needles by means of a spring when the extraction head is in the open position. Such a construction is relatively complex. Furthermore, it requires providing openings with a closed section for the passage of water either through the plate supporting the needles or through the needles themselves, which leads to problems of reduction of the orifices, and blocking or furring up on intensive use of a device. Over time, the flow rates, the through pathways, the volume of water, and other parameters relating to the extraction conditions, in particular the extraction pressure, the extraction time, and the temperature, undergo significant alterations which impair the quality of the extract produced.
Thus, improved devices for extracting foodstuffs are needed, and these are now provided by the present invention.